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| author | Dan Carpenter <dan.carpenter@oracle.com> | 2017-08-18 13:30:30 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-08-29 11:55:15 +0200 |
| commit | eaa2f87c6b840b83827c40db6eb8481689570259 (patch) | |
| tree | 93449daec7e592149122d621150d06cb79ef6baf | |
| parent | 9c3a815f471a84811cf8021cf64aae3b8081dfde (diff) | |
| download | op-kernel-dev-eaa2f87c6b840b83827c40db6eb8481689570259.zip op-kernel-dev-eaa2f87c6b840b83827c40db6eb8481689570259.tar.gz | |
x86/ldt: Fix off by one in get_segment_base()
ldt->entries[] is allocated in alloc_ldt_struct(). It has
ldt->nr_entries elements and ldt->nr_entries is capped at LDT_ENTRIES.
So if "idx" is == ldt->nr_entries then we're reading beyond the end of
the buffer. It seems duplicative to have two limit checks when one
would work just as well so I removed the check against LDT_ENTRIES.
The gdt_page.gdt[] array has GDT_ENTRIES entries.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-janitors@vger.kernel.org
Fixes: d07bdfd322d3 ("perf/x86: Fix USER/KERNEL tagging of samples properly")
Link: http://lkml.kernel.org/r/20170818102516.gqwm4xdvvuvjw5ho@mwanda
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/events/core.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index af12e29..9390501 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2335,12 +2335,9 @@ static unsigned long get_segment_base(unsigned int segment) #ifdef CONFIG_MODIFY_LDT_SYSCALL struct ldt_struct *ldt; - if (idx > LDT_ENTRIES) - return 0; - /* IRQs are off, so this synchronizes with smp_store_release */ ldt = lockless_dereference(current->active_mm->context.ldt); - if (!ldt || idx > ldt->nr_entries) + if (!ldt || idx >= ldt->nr_entries) return 0; desc = &ldt->entries[idx]; @@ -2348,7 +2345,7 @@ static unsigned long get_segment_base(unsigned int segment) return 0; #endif } else { - if (idx > GDT_ENTRIES) + if (idx >= GDT_ENTRIES) return 0; desc = raw_cpu_ptr(gdt_page.gdt) + idx; |
